A lithium ion secondary battery (hereinafter referred to as LIB) is widely used for portable electronic instruments such as cell phones or notebook-size personal computers. As a cathode material for a LIB, a composite oxide of lithium with e.g. a transition metal (hereinafter referred to as a lithium-containing composite oxide), such as LiCoO2, LiNiO2, LiNiO0.8Co0.2O2 or LiMn2O4, is employed.
In recent years, a LIB started being used for e.g. an electrical power supply for a vehicle. Specifically, a LIB started being used as an electrical power supply for an electric vehicle (EV), a hybrid electric vehicle (HEV) and a plug-in hybrid vehicle (PHEV) driven by a motor and an electrical power supply for idling stop. Further, a LIB for vehicles is required to have higher performance with respect to the capacity, the safety, the output characteristics and the cycle durability as compared with conventional applications.
At present, LiMn2O4 which started being used as a cathode material for a LIB for vehicles has high output characteristics and safety but has problems in a short cruising distance since the capacity is so low as at a level of 120 mAh/g.
Whereas, a cathode material containing Ni, Co and Mn as transition metals (hereinafter referred to as ternary cathode material) such as LiNi1/3Co1/3Mn1/3O2, LiNi0.4Co0.3Mn0.3O2 or LiNi0.5Co0.2Mn0.3O2, which can realize a capacity at a level of 160 mAh/g, is expected as a next-generation cathode material for a LIB for vehicles.